Field of the Invention
The present invention relates to a method for producing a compound having a colorant structure, suitable as a pigment dispersant, a pigment dispersant containing the compound, a pigment composition containing the pigment dispersant, and a pigment dispersion and a toner containing the pigment composition.
Description of the Related Art
A pigment having a small particle size generally tends to be strong in the aggregation force between pigment particles, and therefore, dispersing thereof in a medium such as an organic solvent and a molten resin is easily insufficient. A pigment, if being insufficient in dispersibility, has a reduced tinting power.
As a dispersant having a high dispersibility, a dispersant has been heretofore used in which a compound having a high affinity with a pigment is bound to a terminal of a polymer that imparts dispersibility in a medium. For example, Japanese Patent Application Laid-Open No. 2012-077297 discloses, in order to enhance dispersibility of a pigment in a toner, an example of use of a dispersant in which a colorant compound having a high affinity with a pigment is bound to a terminal of a polymer obtained by radical polymerization using a thiol type chain transfer agent, as well as a method for producing such a dispersant.
Thus, in order to enhance dispersibility of a pigment in a toner particle, various polymer dispersants in toners of respective colors of yellow, magenta, cyan and black, and production methods thereof have been proposed.
Japanese Patent Application Laid-Open No. 2012-067285 discloses, in order to enhance dispersibility of an azo type pigment in a yellow toner, a dispersant having a compound having an azo backbone structure and a production method thereof.
In addition, Japanese Patent Application Laid-Open No. 2006-030760 discloses, in order to enhance dispersibility of a magenta pigment in a magenta toner, use of a specific polyester type dispersant.
In addition, Japanese Patent Application Laid-Open No. H03-113462 discloses, in order to enhance dispersibility of a phthalocyanine pigment in a cyan toner, use of a polymer containing sodium styrene sulfonate as a monomer unit, as a dispersant.
In addition, Japanese Patent Application Laid-Open No. H06-148927 discloses, in order to enhance dispersibility of carbon black in a black toner, use of a copolymer of a styrene type monomer and an acrylate type (or methacrylate type) monomer, as a dispersant.